The throttle position sensor on your 3.0L V6 equipped Honda Accord (Acura CL) can be accurately tested without a scan tool. How? by using a simple multimeter.
In this tutorial, I'll show you how in a step-by-step way so that you can conclude that the TPS is fried or is OK.
Contents of this tutorial:
Symptoms Of A Bad Throttle Position Sensor
The throttle position sensor's job is to tell your Accord's PCM how much the throttle plate opens/closes as you step on/step off the accelerator pedal to accelerate the engine/vehicle.
The PCM then uses this throttle plate angle info to inject more or less fuel (among several things). Being that this sensor is such a critical component of your Honda's engine management system, when it fails you'll see one or more of the following symptoms:
- Check engine light (CEL) is illuminated on your Accord's instrument panel.
- A TPS diagnostic trouble code (DTC) stored in the PCM's memory:
- P0120: Throttle Position Sensor Circuit Malfunction.
- Bad gas mileage.
- Hard start and/or extended cranking time (after shut off).
- Black smoke coming out of the tailpipe.
- Hesitation when accelerating your vehicle down the road.
TEST 1: Testing The Throttle Position Sensor Voltage Signal
In a nutshell, the TPS converts the throttle plate angle (as you step on/step of the accelerator) into an analog voltage signal. Your 3.0L Accord's PCM then receives this throttle position signal on the wire that connects to terminal #2 (middle wire) of the throttle position sensor's connector (see illustration above).
This signal is very easy to measure with a simple multimeter. To be a bit more specific: what we'll do is see if the TPS creates an increasing voltage signal as we open the throttle plate to its Wide Open Throttle (WOT) position. This voltage signal should then decrease back to its original voltage when we slowly close the throttle plate (back to its closed position).
NOTE: The throttle position sensor has to remain connected to its connector for this test to work (this is where a wire piercing probe comes in handy to get to the signal inside the wire. To see what one looks like, click here: Wire Piercing Probe Tool.)
You can see this test step performed in this YouTube video: How To Test The TPS (1997, 1998, 1999, 2000, 2001 2.0L Honda CR-V) (NOTE: Although this video applies to the 1997-2001 2.0L Honda CR-V, the test procedure itself is the same for the 1998-2002 3.0L Honda Accord).
OK, let's start:
Place your multimeter in Volts DC mode and with the RED multimeter lead probe the middle wire of the sensor's connector. This is the wire that connects to TPS pin #2 in the illustration above.
Ground the black multimeter test lead on the battery negative terminal. Have you helper turn the Key On, but don't start the engine (this will power up the TP sensor).
Your multimeter should report a voltage between .2 to .9 Volts DC. If your multimeter doesn't, don't worry about it just yet, continue with the other steps.
Now, slowly open the throttle (by hand and from the engine compartment) while you observe the change in voltage numbers on your multimeter.
For this test result to be accurate, you need to open the throttle by hand and not from inside the vehicle.
As the throttle opens, the voltage numbers will increase. This increase in voltage should be smooth and without any gaps or skips. Once the throttle is wide open, your multimeter should read somewhere between 3.5 to 4.5 Volts DC.
Now, slowly close the throttle. As the throttle is closing, you should see the voltage decrease smoothly and without any gaps or skips, to the exact same voltage you noticed in step 4.
OK, now you'll need someone to help you lightly tap on the throttle position sensor with the handle of a screw-driver (or something similar, and I want to emphasize the words ‘lightly tap’) as you slowly open and close the throttle and observe the multimeter.
If the TPS is bad, the tapping will cause the voltage numbers to skip or go blank. If the TPS is OK, the tapping will have no effect on the voltage numbers.
Repeat step 7 several times to make sure of your multimeter test results.
Let's take a look at your test results:
CASE 1: The voltage increased/decreased as you manually opened/closed the throttle plate. This means that your 3.0L equipped Honda's throttle position sensor is OK (not defective).
CASE 2: The voltage DID NOT increase/decrease as you manually opened/closed the throttle plate. This tells you that the throttle position sensor (TPS) on your 3.0L Honda has a problem.
Before condemning the TPS to the scrap heap, you need to make sure that it's getting both power and Ground. To check for power, go to: TEST 2: Verifying Throttle Position Sensor Has Power.
CASE 3: Multimeter DID NOT register any voltage. This test result doesn't condemn the TP sensor as BAD just yet. Why? Because the TP sensor may be missing either power or Ground.
So the next step is to check that the TP sensor is getting power, go to TEST 2: Verifying Throttle Position Sensor Has Power.